During the construction of such insulating glass units, units of varying size are filled with heavy gas one after the other using the same filling apparatus. The costs of the filling depend, on the one hand, upon the total time required for the complete filling with heavy gas and, on the other hand, upon the total quantity of heavy gas required for the filling. Losses of heavy gas can especially occur in that during the introduction of the heavy gas into the initially, after construction of the unit, air-filled interior space, turbulent mixing between the heavy gas and the air takes place which becomes more pronounced the more quickly the heavy gas is introduced. The portion of the introduced heavy gas mixed in this manner with the air must now also be as fully as possible replaced with unmixed heavy gas as otherwise an insufficient sound and heat insulation will result.
A procedure for filling the interior space of an insulating glass unit with nitrogen is known from U.S. Pat. No. 2,756,467, in which dried nitrogen is introduced through the bottom end and the air is evactuated from the top end. Simultaneously, the pressure in the interior space of the insulating glass unit is monitored and the filling and evacuation rate is regulated so that there is constantly a small negative pressure in the interior space. The problems of the filling rate as well as of the turbulent mixing of the filling gas with the air are here neither mentioned nor solved.
From EP No. 0 046 847, which goes back to the same inventors as the present invention, an automation of the filling procedure is proposed through the control of the filling and/or evacuation rate depending upon the measured pressure. Because of the surety of the automatic control, the filling rate can be raised without danger of excess pressure in the interior space and breakage of the insulating glass unit so far, that a decrease of the filling time of at least 30% is achieved. Also this known procedure is only concerned with the prevention of glass breakage during a faster filling and not with the problem of losses introduced with the turbulent mixing.